Field of the Invention
The invention relates to a device for printing on at least one region of a surface of an object, in which the device includes a manipulator with a print head.
The technical field of the invention is the field of printing on so-called 3D surfaces by using inkjet printing processes. In general, such surfaces include regions that are not flat but curved.
Description of the Related Art
German Application DE 10 2012 006 371 A1, corresponding to U.S. Application US 2015/0042716, discloses a technical configuration for printing on 3D surfaces wherein a manipulator such as an articulated robot guides a print head along the surface of the object to be printed in multiple adjacent strips and at a printing distance.
German Application DE 10 2012 006 370 A1, corresponding to U.S. Pat. No. 8,882,242 and German Application DE 10 2013 019 359.1, corresponding to U.S. application Ser. No. 14/547,365, filed Nov. 19, 2014, disclose technical configurations that ensure that the strips adjoin in an error-free way and are thus invisible to the human eye.
Due to the fact that vibration of the manipulator and consequently of the print head that is guided by the manipulator cannot be avoided, adjacent ink droplets (print dots) or ink droplets that are deposited on top of one another—for instance to create CMYK color prints—may be imperfectly positioned on the surface, resulting in a flawed printed image. An elimination of such vibration by changing the construction of the manipulator itself would be very difficult and expensive and often basically impossible because the manipulator is a standard industrial robot and a purchased part. In addition, the problem depends on the size of the manipulator, which means that it may arise in particular when large objects such as auto body parts are to be printed on.
European Application EP 1 001 184 A2, corresponding to U.S. Pat. No. 6,269,093, discloses a machining device including a manipulator with three linear axes and a tool head. Vibrations of the manipulator are detected by a sensor and are compensated for by using an actuator. The linear actuator is disposed on the last linear axis in front of the tool.
Japanese Application JP H 06 262 583 likewise discloses a manipulator with sensor-controlled vibration compensation for a gripper. The gripper is fixed to a vibration damper, which is disposed on the last arm of the manipulator. The vibration damper has a movable mass.
The human eye is very perceptive and realizes even minute flaws in a printed image. Thus vibration of the print head during a printing process needs to be avoided. The vibration energy of a system is a function of its vibrating mass. When the active component is directly connected to the manipulator, strong adjustment forces are required to attain sufficient vibration reduction.